Scr motor speed control with plug sensing circuit

ABSTRACT

A control system for controlling energy directed from a power source to a DC variable speed motor includes a main SCR, series connected with the motor, an oscillator, a sawtooth generator, a reference operational amplifier, and a firing pulse generator. The output of the sawtooth generator is summed with the output of the reference operational amplifier and directed to the firing pulse generator. When the summed output of the reference operational amplifier and the sawtooth generator exceeds the threshold voltage of the firing pulse generator, the firing pulse generator will fire to effect conduction of the main SCR to direct energy to the motor. A commutating circuit is provided for turning the main SCR off during each cycle of the oscillator. The commutating circuit includes a secondary SCR and a LC resonant circuit both of which are parallel connected to the main SCR. The LC resonant circuit acts to reverse bias the main SCR upon conduction of the secondary SCR. A regulated power supply is also provided to energize the various components of the control system. The regulated power supply includes a negative power supply which comprises an astable multivibrator and a diodecapacitor matrix for directly converting a positive voltage to a regulated negative voltage.

i 7 7' Inventor:

Jan. 9, 1973 [54] SCR MOTOR SPEED CONTROL WITH PLUG SENSING CIRCUITvard, KenOs'ha,'-Wis. 5 31 1 0 [7 3] Assigriee: Eaton Corporation [22]Filed: A ril 6,1971

21 Appl. No.: 131,624

52 U.S. Cl. ..3l8/373 [51] Int. Cl. .1102]! 3/10, H02p 5/16 1 [58] Fieldof Search.....32l/45 C; 318/284, 293, 300,

[56] References Cited UNITED STATES PATENTS 3,437,826 4/1969 Kelley..318/341 3,344,328 9/1967 MOi'i'iB ..318/373 3,562,611 2/1971 Gurwicz321/45 C 3,436,632 4/1969 Tisserant ..318/284 3,500,i6l 3/1970 Domann..3l8/34l 3,582,763 6/1971 Huber 321/45 C Primary Examiner-Bernard A.Gilheany Assistant Examiner-Thomas Langer Attorney-Teagno & Teddy andEaton Yale & Towne Inc.

Aubrey H. Smith, Pershing'i Boule- A control system for controllingenergy directed from a power source to a DC variable speed motorincludes a main SCR, series connected with the motor, an oscillator,- asawtooth generator, a reference operational amplifier, and a firingpulse generator. The output of the sawtooth generator is summed with theoutput of the reference operational amplifier and directed 'to thefiring pulse generator. When the summed outi put of the referenceoperational amplifier and the saw- ,tooth generator exceeds thethreshold voltage of the firing pulse generator, the firing pulsegenerator will tire to effect conduction of the main SCR to directenergy to the motor. A commutating circuit is provided for turning themain SCR off during each cycle of the oscillator. The commutatingcircuit includes a secondary SCR and a LC resonant circuit both of whichare parallel connected to the main SCR. The LC resonant circuit acts toreverse bias the main SCR upon conduction of the secondary SCR. Aregulated power supply is also provided to energize the variouscomponents of the control system. The regulated power supply includes anegative power supply which comprises an astable multivibrator and adiode-capacitor matrix for directly converting a positive voltage to aregulated negative voltage.

14 Claims, 10 Drawing Figures SCR MOTOR SPEED CONTROL WITH PLUG SENSINGCIRCUIT The present invention relates to a control system forcontrolling energy directed from a power source to a load and morespecifically to a control system utilizing a controlled rectifier forcontrolling the flow of energy from the power source to a variable speedmotor.

Control systems are known in the art for controlling energy applied to avariable speed motor from a power source. Some known control systemsutilize controlled rectifiers which are fired at an adjustable frequencyto control the speed of the motor. This type of system suffers from thedisadvantage that when slow speeds are desired, the motor is pulsed veryslowly and does not run smoothly. Other known systems utilize very highfrequency firing of the controlled rectifiers to alleviate theaforementioned problem. However, when very high frequency firing of thecontrolled rectifier is utilized power dissipation from the controlledrectifier becomes a problem and overheating often occurs.

Accordingly, it is an object of the present invention to provide a newand improved control system for controlling the energy directed from apower source to a load utilizing a controlled rectifier and wherein theforegoing problems are alleviated.

Another object of the present invention is to provide a new and improvedcontrol system for controlling the energy directed from a power sourceto a load including a main SCR series connected with the load which isintermittently pulsed to an on condition to control the energization ofthe load and a commutating circuit including a secondary SCR connectedin parallel with the main SCR and a LC resonant circuit connected inparallel with the secondary SCR. The LC circuit normally charges to afirst polarity and discharges, upon conduction of the secondary SCR to asecond polarity opposite the first polarity. The LC circuit whendischarging reverse biases the main and secondary SCRs to render theSCRs nonconductive.

A further object of the present invention is to provide a new andimproved control system for controlling the energy directed from a powersource to a load including a regulated negative power supply comprisingan astable multivibrator and a diode-capacitor matrix connected to theastable multivibrator for inverting the positive voltage supplied to theastable multivibrator directly to a regulated negative voltage.

Still another object of the present invention is to provide a new andimproved control system for controlling energy directed from a powersource to a motor including controlled rectifying means connected to themotor for controlling the energization thereof, pulse generating meansfor generating repetitive pulses of a predetermined period, firing pulsegenerating means connected to the pulse generating means for renderingthe controlled rectifying means conductive at a predetermined timeduring each of the predetermined periods, commutating circuit means forrendering the controlled rectifying means nonconductive at the end ofeach of the predetermined periods, ramp generating means for generatinga ramp signal upon acceleration of the motor from a zero speedcondition, speed and direction sensing means, first control means forcontrolling the direction of rotation and the speed of the motor, thespeed and direction sensing means effecting a zero output from the rampgenerating means when the speed and direction sensing means senses therotation of the motor to be opposite the direction of rotation calledfor by the first control means, second control means having an inputfrom the ramp generating and an output connected to the firing pulsegenerating means to control the period of conduction of the controlledrectifying means, the controlled rectifying means being nonconductivewhen the second control means has an output below a predetermined level,dynamic braking means responsive to the speed and direction sensingmeans for applying an input to the second control means when the speedand direction sensing means senses the direction of rotation of themotor to be opposite the direction of rotation called for by the firstcontrol means to enable the second control means to effect conduction ofthe controlled rectifying means at a predetermined level to therebydynamically brake the rotation of the motor, power supply meansconnected to the power source for applying predetermined potentials andbypass means for rendering the controlled rectifying means nonconductiveand connecting the power source directly to the motor when the firstcontrol means is actuated to a full speed condition.

Another object of the present invention is to provide a new and improvedcontrol system for controlling energy directed from a power source to aload including first controlled rectifying means, second controlledrectifying means connected in parallel to the first controlledrectifying means, energy storage means c0nnected in parallel to thesecond controlled rectifying means for applying a potential to the firstand second controlled rectifying means to render the first and secondcontrolled rectifying means nonconductive, means for charging the energystorage means to a first polarity, and means for rendering the secondcontrolled rectifying means conductive for discharging the energystorage means through the second controlled rectifying means causing theenergy storage means to be charged to a second polarity opposite thefirst polarity and wherein the energy storage means when charged to thesecond polarity applies the potential to the first and second controlledrectifying means to thereby render the first and second controlledrectifying means nonconductive.

A further object of the present invention is to provide a power supplyfor producing a regulated voltage including a power source, an astablemultivibrator having a first gate and a second gate, each of the gatesbeing connectable to the power source and having first and second outputconditions, the first gate having the first output condition when thesecond gate has the second output condition and the first gate havingthe second output condition when the second gate has the first outputcondition, first energy storage means connected to the output of thefirst gate, second energy storage means connected to the output of thesecond gate third energy storage means connected to the first and secondenergy storage means and operable to apply a predetermined voltage, thefirst energy storage means charging when the first gate is in the firstcondition and discharging when the first gate is in the secondcondition, the second energy storage means charging when the second gateis in the first condition and discharging when the second gate is in thesecond condition, the third energy storage means being charged by thefirst energy storage means when the first gate is in the secondcondition and being charged by the second energy storage means when thesecond gate is in the second condition, the third energy storage meansbeing charged by the first and second energy storage means to thepredetermined voltage and voltage regulating means connected across thethird energy storage means for regulating the voltage applied by thethird energy storage means.

Further objects and advantages of the present invention will becomeapparent fm .e following detailed description of the present inventiontaken in conjunction with the following drawings wherein:

FIG. 1 is a schematic block diagram illustrating present invention;

FIG. 2 is a schematic illustration of the positive power supply;

FIG. 3 is a schematic illustration of the negative power supply;

FIG. 4 is a schematic illustration of the reference operationalamplifier;

FIG. 5 is a schematic illustration of the main SCR and the commutatingcircuit;

FIG. 6 is a graphical illustration showing the output ofthe oscillatorand the RC sawtooth generator;

FIG. 7 is a graphical illustration of the output of the firing pulsegenerator and the output of the sawtooth generator combined with theoutput the reference operational amplifier;

FIG. 8 is a schematic illustration similar to FIG. 7 illustrating thefiring pulse generator output and the saw tooth generator output whencombined with a reference operational amplifier output which is largerthan that illustrated in FIG. 7;

FIG. 9 is a graphical illustration showing the RC sawtooth generatoroutput and the output of the commutating pulse generator; and

FIG. 10 is a graphical illustration of the output of the reference rampgenerator showing the output thereof when a plug is sensed.

The present invention relates to a control stem for controlling energydirected from a power source to a motor. A controlled rectifier means,preferably a SCR, is connected between the motor and the power sourcefor controlling the energization of the motor. A firing pulse generatoris connected to the gate of the SCR for firing the SCR at predeterminedtimes to effect a pulse width modulation of the power source applied tothe motor to thereby control the speed of the motor. A commutatingcircuit including a second controlled rectifier, preferably a secondSCR, is connected in parallel with the fir SCR to effect switching ofthe first SCR from a conductive to a nonconductive condition. Associatedwith the firing pulse generator and the commutating circuit is variouscontrol circuitry for optimizing the control of the motor. A regulatedpower supply is provided for energizing the various control circuitry.

The present invention illustrated in FIG. I is utilized in conjunctionwith a DC variable speed motor 10. The motor 10 may be used in variousembodiments but is preferably used for driving a vehicle such as aforklift truck. The motor 10 has connected to one terminal thereof abattery 12. Connected to the opposite side of the motor 10 are contacts14, 16, 18, and 20 which control the polarity of the voltage developedacross the field 22 of the motor 10 to thereby control the direction ofrotation of the motor. The contacts 14 and 16 are respectively closedand opened when the field of the motor is energized to effect rotationof the motor 10 in a reverse direction and contacts 18 and 20 arerespectively closed and opened when the field 22 is energized to effecta rotation of the motor 10 in a for ward direction.

Series connected to the motor 10 is a main SCR 24.

When the SCR 24 is conductive a circuit is completed from the battery12, through the motor 10, through closed contact 14 or 18, through thefield 22, through the closed contact 16 or 20 and through the SCR 24 tothe ground 26 to thereby effect rotation of the motor 10 in a directiondetermined by the closed ones of the contacts l4-18. The speed of themotor 10 is controlled by pulsing the SCR on and off for predeterminedperiods of time. The longer the period of time that the SCR 24 conductsthe greater will be the speed of the motor 10 and conversely, theshorter the period the SCR 24 conducts the slower the speed of the motor10. Thus, closing of certain of the contacts 14l8 control the directionof rotation of the motor 10 and the period of conduction of the main SCR24 controls the speed of the motor by pulse-width modulating the ener'gy applied to the motor by the battery 12.

The firing or conduction of the SCR 24 is controlled by a firing pulsegenerator and amplifier 28 which is operable to apply pulses atpredetermined times to the gate 30 of the SCR 24. As is known in the artwhen a pulse applied to the gate of sawtooth generator SCR and the anodeis positive with respect to the cathode, the SCR will be renderedconductive. An oscillator 32, a RC sawtoothenerator 34 and a referenceoperational amplifier 36 control the input to the firing pulse generatorand amplifier 28 to control the period of con duction of the SCR 24. Theoscillator 32 is preferably a 200-Hz oscillator which is well known theart and which produces a square wave output as is shown in FIG 6. Theoutput of the oscillator 32 is fed to the RC sawtooth generator 34 whichproduces a sawtooth wave, illustrated in FIG. 6, having a frequency ofthe same frequency as the output of oscillator 32. The output of the RCsawtooth generator is applied to a summing junction 38 along with outputof the reference operational amplifier 36. The output of the referenceoperational amplifier 36 is a DC output which is added to the sawtoothwave output of the RC sawtooth generator 34 at the summingjunction 38.The combined signal of the sawtooth generator and DC output of amplifier36 are applied to the firing pulse generator 28. The firing pulsegenerator and amplifier 28 is triggered when the threshold voltagethereof is reached at the summing junction 38 to there apply a firingpulse to the gate 30 of the SCR 24 to effect conduction thereof.

The level of the DC output of the reference rational amplifier 36controls the point at which the output of summing junction 38 exceedsthe threshold voltage of the firing pulse generator 28. For example, thefiring pulse generator will be fired earlier in a cycle if the magnitudeof the DC output from amplifier 36 is high. Conversely, the firing pulsegenerator 28 will be fired later in a cycle if the magnitude of the DCoutput from amplifier 36 is lower. FIGS. 7 and 8 graphically illustratethe output of the firing pulse generator 28 and the output of thesummingjunction 38, which is the output of the RC sawtooth generator 34having the DC output of the reference amplifier 36 added thereto. InFIG. 7 the operational amplifier 36 has a first DC output level whichcauses the sawtooth wave to exceed the threshold voltage of the firingpulse generator 28 at the points schematically illustrated as 40 so asto effect an output from the firing pulse generator 28 schematicallyillustrated as the pulse 41. In FIG. 8 the output of the referenceoperational amplifier 36 has been increased over that illustrated inFIG. 7 and the sawtooth wave exceeds the threshold voltage of the firingpulse amplifier 28 at a point 42 which precedes the point 40 as shown inFIG. 7. When the sawtooth wave exceeds the threshold voltage at thepoint 42, the firing pulse generator 28 initiates an output pulse 43 toaffect conduction of the SCR 24. Thus, the point, during each cycle ofthe sawtooth wave at which the firing pulse generator 28 fires the SCR24 is controlled by the DC output level of the reference amplifier 36.

The output of oscillator 32 is also fed to a commutating pulse generatorand amplifier 44. The output of the commutating pulse generator andamplifier 44 is a pulsating output wherein the pulses occursimultaneously with the end of each cycle of the sawtooth wave of thesawtooth generator 34. This is schematically illustrated in FIG. 9. Theoutput of the commutating pulse generator is then directed to acommutating circuit 46 which is operable to reverse bias the SCR 24,thereby making the cathode positive with respect to the anode thereof torender the SCR 24 nonconductive.

It should be appreciated that the firing pulse generator and amplifier28 turns the SCR 24 on once during each cycle of the oscillator 32 andthat the commutating pulse generator and amplifier 44 and commutatingcircuit 46 turn the SCR 24 off at the end of each cycle of theoscillator 32. This effects pulse-width modulation of the output of thebattery 12 through the 10. The point at which the SCR 24 starts toconduct controls the period of conduction of the SCR 24 during eachcycle. Thus, an increased output from the operational amplifier 36causes the SCR 24 to conduct earlier during each cycle of the oscillator32 and for a longer period of time, since the SCR 24 is not turned offuntil the end of the cycle of the oscillator 32. Conversely, a decreasein the output of the reference operational amplifier 36 causes the SCR24 to turn on later during a cycle of the oscillator 32 and accordinglythe period of conduction of the SCR 24 is decreased. The period ofconduction of the SCR controls the speed of the motor by pulse-widthmodulating the power applied thereto from battery 12.

The reference operational amplifier 36 receives a DC input from areference ramp generator and reacceleration rate circuit 50 via anaccelerator pedal potentiometer 52. The output of the reference rampgenerator 50 is generally a linear output which is substantiallyconstant under normal operating conditions. The constant output of thereference ramp generator, which is shown by the portions 62 of the curveillustrated in FIG. 10, is directed to the accelerator pedalpotentiometer 52 which taps off a portion of the reference voltage fromthe reference ramp generator 50 and directs the output therefrom to thepositive input of the reference operational amplifier 36 via the summingjunctions 56 and 60. The accelerator pedal potentiometer 52 is attachedto the accelerator pedal of the vehicle and the portion of the output ofthe reference ramp generator 50 which the accelerator pedalpotentiometer 52 directs to the reference amplifier 36 is proportionalto the position of the accelerator pedal and hence the speed of thevehicle. Thus, the signal from the reference ramp generator 50 asmodified by the accelerator pedal potentiometer 52 has a magnitude whichis proportional to the desired speed of the vehicle as indicated by theposition of the accelerator pedal. This output from the reference rampgenerator 50 normally controls the DC output from the referenceoperational amplifier 36 to thereby control the firing pulse generatorand amplifier 28.

A maximum current limit circuit 64 is provided to see the currentflowing in the motor 10 and prevent a predetermined maximum current frombeing exceeded. The maximum current limit circuit 64 senses a voltagedeveloped across a resistor 66 which is series connected with the SCR24. The voltage developed across resistor 66 is directly proportional tothe motor current. The voltage developed across resistor 66 is directedacross a current feedback resistor 68 and a certain percentage of thisvoltage applied to the negative input of an operational amplifier 70.The operational amplifier 70, schematically illustrated in FIG. 1preferably has associated therewith feedback circuitry, not illustrated,which enables the output of the operational amplifier 70 to be anegative DC voltage proportional to the average value of the motorcurrent. The negative output of the operational amplifier 70 is summedat the summing junction 60 with the DC output of the reference rampgenerator 50 as modified by the accelerator pedal potentiometer 52 andthen directed to the positive terminal of the reference operationalamplifier 36. The output of the maximum current limit circuit 64 is anegative DC voltage which is offset against the positive output of thereference ramp generator 50 at the summing junction 60. The currentfeedback signal from the maximum current limit circuit 64 acts to limitthe current flowing through the motor 10 by applying an increasingnegative voltage to the summing junction 60 as the current through themotor 10 increases to thereby limit the output of the referenceoperational amplifier 36 and the period of conduction of SCR 24. Themaximum current limit can be controlled by varying the arm of thecurrent feedback resistor 68.

A minimum current circuit 72 provides an input at the negative inputterminal of the reference operational amplifier 36. The minimum currentcircuit 72 which includes the potentiometer 74 applies a signal to biasthe operational amplifier 36 so that when no signals are present at thepositive input of the amplifier 36, the output of the amplifier 36 whenadded to the output the RC sawtooth generator 34 at the summing junction38 will be just below the threshold level of the firing pulse generatorand amplifier 28.

A plug sensing circuit 76 is provided to sense when the vehicle istraveling in a direction opposite to that called for by the closing ofthe appropriate contacts 14-18. When the vehicle is in normal operation,traveling in a first direction and the polarity of current flow throughthe motor field 22 is reversed to reverse the direction of the motor byopening and closing the appropriate contacts 14-18 without stopping thevehicle, the vehicle will continue to travel in the first direction dueto the inertia of the vehicle. The plug sensing circuit 76 will sensethat the vehicle is traveling in the direction opposite to that calledfor by the contacts 14-18. The plug sensing circuit 76 senses thecurrent passing through the diode 78. Normally, when the vehicle istraveling in the direction called for by the contacts 14-18 the currentflow through diode 78 will be of a predetermined magnitude. When thevehicle is moving in a direction opposite to the direction called for bythe contacts l418, the motor 10 will be driven by the vehicles motionand will act as a generator pumping current through the free wheelingdiode 78. The current flowing through the diode 78 will be of a largemagnitude relative to the predetermined magnitude of the current flowingthrough the diode 78 when the motor 10 is rotating in the connectdirection. The plug sensing 76 senses the magnitude of the volt ageacross the diode 78 to determine if a plug, i.e., travel of the vehiclein a direction opposite to the direction called for by the contactsl4-18, occurs. Upon occurrence of a plug, the plug sensing circuit 76will apply a signal to the reference ramp generator 50 which causes theoutput of the reference ramp generator 50 to go to zero, as isgraphically illustrated in FlG. 10.

The output of the referee ramp generator 50 is sensed by a dynamicbraking and plug severity circuit 80. When the output of the referenceramp generator 50 drops to zero, the dynamic braking circuit 80 willactivated to apply a small voltage to the positive input of thereference operational amplifier 36 via the summing junctions 56 and 60.The output of reference ramp generator 50 will remain at a zero level aslong as a plug is sensed by the dynamic braking and plug severitycircuit 80. When the vehicle comes to a stop and a plug is no longersensed the ramp generator will generate a ramp signal illustrated at 82in FIG. 10. The dynamic braking circuit 80 will continue to apply aninput to the reference operational amplifier 36 until the output of thereference ramp generator 50 returns substantially to its original valueindicated by the portion 62 of the curve of FIG. 10. Thus, duringreacceleration of the vehicle a signal will be applied to the referenceoperational amplifier 36 by both the ramp generator 50 and the dynamicbraking and plug severity circuit 80.

The small voltage applied to the positive input of the referenceoperational amplifier 36 by the dynamic braking circuit 80 when thevehicle is traveling in a direction opposite that called for by thecontacts l4 l8 enables the amplifier 36 to have an output signal whichwill effect continued firing of the firing pulse generator and amplifier28. The firing of the firing pulse generator and amplifier 28 while themotor 10 is acting as a generator effects a small current flow throughthe motor 10 which tends to dynamically brake the motor since thevoltage applied to the motor will tend to effect rotation of the motorin a direction opposite to that which the motor is rotating by theinertia of the vehicle. Thus, the dynamic braking circuit 80 dynamicallybrakes the vehicle and the motor to a smooth stop before it isreaccelerated in the opposite direction. When the vehicle comes to astop and the output from the reference ramp generator 50 reaches itsapproximate normal maximum value, as indicated by the portions 62 of thecurve in FIG. 10, the output from the dynamic braking circuit disappearsand the vehicle will travel in the direction opposite to which it haspreviously been going.

When the vehicle is running at full speed it is desirable to eliminatethe 200-Hz switching of the motor current and instead apply full batterypotential to the motor 10. Accordingly, a bypass circuit 86 is provided.The bypass circuit 86 is operable to sense the output of the referenceramp generator 50 and the position of the accelerator pedal of thevehicle. It should be appreciated that when it is desired to run thevehicle at full speed two conditions will be fulfilled, i.e., namely,the acceleration pedal will be fully depressed and the output of thereference ramp generator 50 will be at its maximum. When the acceleratorpedal is fully depressed, an accelerator switch 82 will be closed. Whenthe accelerator switch 82 is closed and the output of the reference rampgenerator 50 is at approximately its maximum output, the bypass circuit86 will energize a coil 88 of a relay to close the contact 88a of therelay which is connected in parallel to the SCR 24. Closing of thecontacts 88a will enable the battery 12 to apply full power to the motor10 so that the vehicle will run at full speed. The bypass circuit 86also applies an input to a delay circuit 90 which shuts down the rest ofthe control system during full speed operation of the vehicle.

When relays are utilized as switches to control the energization of themotor 10 there is a short period after the relays are closed in whichthey do not make continuous contact. During this period the contacts ofthe relays bounce and therefore delay circuit 90 is utilized to preventenergization of the control system until after the contacts have stoppedbouncing. The delay circuit 90 operates upon energization thereof toprevent energization of the commutating pulse generator and amplifier44, the reference ramp generator 50, the RC sawtooth generator 34, andthe reference operational amplifier 36. The delay circuit preferablyprovides a 200 millisecond delay after the relay contacts 14-18 havebeen closed before the control system may operate. As described above,the delay circuit 90 also functions in response to energization of thebypass circuit 86 to render components of the control system inactiveduring full speed operation of the motor 10.

A regulated power supply 92 is provided to energize the variouscomponents of the control system with voltages schematically illustratedin FIG. 1. The regulated power supply 92 is connected to the positiveterminal of the battery 12 and is operable to apply regulated voltagesto the different portions of the circuitry of the system. The powersupply 92 includes a positive power supply 94 and a negative powersupply 96. The positive power supply 94 has three outputs therefromhaving potentials of plus 12 volts, plus 6.8 volts and 15 volts. Thenegative power supply has a single output of a minus 6.8 volts. The plusand minus 6.8 volts from the power supply 92 are used to energize theoperational amplifiers 36 and 70. The 12 volt output is used to energizethe reference ramp generator 50 and the dynamic braking circuit 80. Theplus 15 volt output of the positive power supply 94 is used to energizethe negative power supply 96, the plug sensing circuit 76, the firingpulse generator and amplifier 28, the commutating pulse generator andamplifier 44, the delay circuit 90, the RC sawtooth generator 34 and theoscillator 32.

The positive power supply 94 which is more fully il lustrated in FIG. 2,includes transistors 98 and 100. Transistor 98 is a series-regulatingvariable-impedance transistor whose conductivity is controlled by thecollector current of transistor 100. A resistor 102 is connected betweenthe emitter of transistor 98 and the emitter of transistor 100. Theresistor 102 limits the amount of current flowing through Zener diode104 which is connected to the emitter of transistor 100. The

current flow through resistor 102 plus the emitter current of transistor100 establishes the reference voltage for the Zener diode 104 which inthis case is plus 6.8 volts. The base of transistor 100 provides afeedback network for the power supply and is connected to a pair ofresistors 106 and 108 which form a voltage divider network having valuessuch that line 1 will always be a plus volts and the base of transistor100 will be at 6.8 volts plus the base emitter voltage drop oftransistor 100. An increase in the potential at the base of transistor100 will tend to decrease the potential at the emitter of transistor 98and a decrease in potential at the base of transistor 100 will tend toincrease the potential at the emitter of transistor 98 to thereby holdline 110 at plus 15 volts. Thus, the transistors 98 and 100 cooperate toform a negative feedback amplifier utilizing Zener diode 104 as areference.

The battery 12 is connected to the positive power supply 94 through adiode 118 which acts as an isolation diode to prevent negative voltagepulses from occurring in the power supply. When positive pulses occur,resistors 119 and 120 cooperate with the capacitor 122 to form a noiseattenuation circuit for the base of transistor 98 and resistors 124 and126 and capacitor 128 form a noise attentuation circuit for thecollector of transistor 98. Since it is desired to utilize the regulated power supply with batteries having different potentials which mayrange approximately from 18 to 80 volts a jumper 130 is provided bybypass resistor 119. Generally, when the power supply 94 is used with abattery 12 having a potential above 36 volts the jumper 130 will not beutilized, but if a battery potential below 36 volts is utilized thejumper 130 will be connected across resistor 119 to isolate the resistorfrom the circuit.

The available outputs of the positive power supply 94 are plus l5 voltsalong line 110, plus l2 volts along line 112, plus 6.8 volts along line114 and ground potential along line 116. The l2 volt output along line112 is obtained by applying the 15 volt supply across the Zener diode132. A resistor 134 is series connected with the Zener diode 132 tolimit the current flow to the Zener diode 132.

Since the present control system utilizes operational amplifiers instable high gain circuits, the provision ofa negative power supply tooperate the amplifiers is critical. The common way of producing anegative power supply is to utilize an inverter to drive a smalltransformer. However, the utilization of a transformer yields a bulkyand costly configuration. The present control system utilizes an astablemultivibrator for driving a diode-capacitor matrix illustrated in FIG.3, which inverts the positive power supplied to the multivibratordirectly to a negative voltage. This method is not only economical butalso requires very little space.

The astable multivibrator includes a pair of NAND gates 142 and 144 eachhaving a plus 15 volt input from the positive power supply 94. A pair ofcapacitors 156 and 148 introduce feedback to the astable multivibra'tor. Resistors 150 and 152 are respectively connected to the input ofthe NAND gate 142 and the NAND gate 144. The resistors 150 and 152 areunequal to assure starting of the multivibrator formed by the NAND gates142 and 144 upon the application of a potential thereto. When the outputof the NAND gate 142 is high, the output of NAND gate 144 will be lowand conversely when the output of NAND gate 144 is high the output ofNAND gate 142 will be low.

Connected to the output of gate 142 is a resistor 154 and a capacitor156. Capacitor 156 is connected through diode 158 to a capacitor 160.Connected to the output of gate 144 is a resistor 162 and a capacitor164. The capacitor 164 is connected to the capacitor through a diode166. When the output of gate 142 is high, the capacitor 156 will charge,to approximately 15 volts with a polarity indicated by the plus sign inFIG. 3, through resistor 154 and through a diode 168 which is connectedto the ground. When the output of gate 142 goes to low or ground, thecapacitor 156 will attempt to discharge through the path including theoutput of gate 142, resistor 154, diode 158 and capacitor 160. Theresult of discharging of capacitor 156 through capacitor 160 is that thecharge on capacitor 156 will be distributed between capacitors 160 and156 according to the law of division of charge for capacitors. Thepolarity of the charge applied to capacitor 160 by capacitor 156 will bethat shown by the plus sign in FIG. 3 associated with capacitor 160.

While capacitor 156 is charging capacitor 160, the NAND gate 144 will bein its high state charging capacitor 164 through the path includingresistor 162 and a diode 170 which is connected to ground. The capacitor164 will be charged to approximately 15 volts with the polarityindicated by the plus sign in FIG. 3 associated with capacitor 164. Whenthe astable multivibrator changes state again and the output of gate 144goes to ground, the capacitor 164 will discharge through the pathconsisting of the output of gate 144, resistor 162, diode 166 andcapacitor 160. The discharging of capacitor 164 will again charge thecapacitor 160 to a polarity indicated by the plus sign in FIG. 3. Thus,it should be apparent that the capacitor 156 will charge capacitor 160during half of the period of oscillation of the astable multivibratorand capacitor 164 will charge capacitor 160 during the other half of theperiod. The result is a full wave output applied to capacitor 160.Connected across capacitor 160 is a Zener diode 172 having its cathodeconnected to the ground line. The Zener diode regulates the output fromcapacitor 160 to line 140, the output line of the negative power supply96. A resistor 174 is connected to the anode of the Zener diode 172 tolimit the current through the diode. Accordingly, the line 140 maintainsa minus 6.8 volt potential thereon from capacitor 160.

For a complete understanding of the operation of the control system itis necessary to understand the operation of the reference operationalamplifier 36 which is the point in the control system where the controlsignals converge. Applied to the positive input terminal of the controlamplifier 36, as is more fully illustrated in FIG. 4, is the referencevoltage from the reference ramp generator 50, dynamic braking feedbacksignal from the dynamic braking circuit 80 and the current limit signalfrom the current limit circuit 64. Applied to the negative inputterminal of the control amplifier 36 is a signal from the delay circuit90 and the minimum current signal from the minimum current circuit 72.The reference operational amplifier 36 introduces a lag in the closedloop system. Its feedback elements include a resistor 180 and acapacitor 178 which are parallel connected to a diode 176. The diode 176acts as a clamping diode to clamp any negative output of the operationalamplifier 36 to prevent the amplifier from saturating in the negativedirection. The output of the operational amplifier 36 is fed to thesumming junction 38 through a resistor 182. A potentiometer 184,connected to a resistor 186, which is connected to the summing junction38 and the resistor 182, limits the maximum DC voltage that can beapplied to the summing junction 38 by the output of the operationalamplifier 36. The potentiometer 184 limits the maximum DC voltage outputof the amplifier 36 to limit the maximum speed of the motor 10. Thelimiting of the output of the amplifier 36 limits the triggering of thefiring pulse generator and amplifier 28 and the period of conduction ofthe main SCR 24 to thereby limit the speed of motor 10.

The main SCR 24, which is turned on by the firing pulse generator andamplifier 28, is commutated or switched off at the end of each cycle ofthe oscillator 32 as described hereinabove. The commutating circuit 46,more fully illustrated in FIG. 5, includes a secondary SCR 190, aninductor 192, a capacitor 194 and a diode 196. For the purposes ofclarity the directional contacts l418 have been eliminated from theschematic illustration in FIG. 5. The secondary SCR 190 is connected ina parallel circuit to the main SCR 24 with the cathode of SCR 190connected to the cathode of the SCR 24. The inductor 192 and capacitor194 are com nected in a parallel circuit across SCR 190. When a pulse isapplied to the gate 30 of the SCR 24, the SCR 24 conducts and thecapacitor 194 is charged positively with respect to the ground throughthe diode 196 and inductor 192. The capacitor 194 and inductor 192 forma LC resonant circuit and the energy stored in capacitor 194 willsubstantially all be transferred to the inductor 192 when the capacitor194 is discharged.

The SCR 190 has its gate 198 connected to the output of the commutatingpulse generator and amplifier 44. When an output is applied to the gate198 of the SCR 190, the SCR 190 will conduct. Conduction of the SCR 190will cause the capacitor 194 to discharge through the inductor 192 andthe SCR 190. The energy which is stored in the inductor 192 takes on theform of a current which must be kept flowing as long as the SCR 190conducts. This current keeps flowing until the capacitor 194 is chargedup to a polarity opposite to the polarity to which the capacitor 194 wasoriginally charged. The capacitor is shown schematically with a plussign in FIG. 5 charged to its opposite or reverse polarity afterconduction of the SCR 190. The charge on the capacitor 194 causes acurrent flow to be applied to the cathodes of both SCRs 24 and 190. Thecurrent flow to the cathodes of SCRs 24 and causes the cathodes thereofto become positive with respect to the anodes thereof. This effectivelyreverse biases the SCRs 24 and 190 causes the cathodes thereof to becomepositive with respect to the anodes thereof. This effectively reversebiases the SCRs 24 and 190 and turns them off to their nonconductivestate. After the SCRs 24 and 190 have been turned off the capacitor 194will recharge in the positive direction with respect to ground throughthe diode 196 to a voltage which is dependent upon the load inductanceand resistance, the value of capacitor 194, the value of inductor 192and the instantaneous value of the current through the load at the timethe SCR 24 is turned off. The diode 196 acts as a blocking diode whenthe capacitor 194 is completely recharged to prevent the capacitor fromdischarging until SCR 190 is in its conductive state. Thus, it should beapparent that the LC circuit formed by the capacitor 194 and theinductor 192 operate upon triggering of the SCR 190 to commutate the SCR24. As described hereinabove this occurs at the end of each cycle of theoscillator 32.

From the foregoing it should be apparent that a new and improved controlsystem for controlling the energy applied from a power source to a loadhas been provided. The control system includes an oscillator, a sawtoothgenerator, a main SCR series connected with the load and a firing pulsegenerator. A reference operational amplifier applies a DC control signalto the firing pulse generator which is summed with the output from thesawtooth generator. When the magnitude of the summed outputs of thereference operational amplifier and the sawtooth generator reaches thethreshold voltage of the firing pulse generator, the firing pulsegenerator will apply a potential to the gate of the main SCR to renderthe main SCR conductive. A commutating pulse generator having an inputfrom the oscillator is connected to a commutating circuit. Thecommutating circuit includes a secondary SCR connected parallel to themain SCR and a LC circuit parallel connected to the secondary SCR. TheLC circuit comprising an energy storage means which upon conduction ofthe secondary SCR discharges and recharges to a polarity opposite to thepolarity of which the LC circuit was originally charged. Reversal of thepolarity of the LC circuit reverse biases the main and secondary SCR tothereby render them nonconductive. The control system further includes aregulated power supply which includes a positive power supply and anegative power supply for energizing the various system components. Thenegative power supply includes an astable multivibrator and adiode-capacitor matrix which operates to directly invert a positivevoltage to thereby provide a negative voltage atthe output terminalthereof.

I now claim:

1. A control system for controlling energy supplied from a power sourceto a motor comprising first controlled rectifying means having aconductive and nonconductive condition connected to the motor forcontrolling the energization thereof, first generating means forgenerating a plurality of repetitive pulses of a predetermined period,second generating means connected to said first generating means fordirecting firing pulses to said first controlled rectifying means torender said first controlled rectifying means conductive at apredetermined time during each of said predetermined periods, thirdgenerating means for generating commutating pulses, commutating circuitmeans responsive to said third generating means for rendering said firstcontrolled rectifying means nonconductive at the end of each of saidpredetermined periods, fourth generating means for generating a rampsignal upon acceleration of the motor from a zero speed condition, firstcontrol means for controlling the direction of rotation and the speed ofthe motor, speed and direction sensing means for affecting asubstantially zero output from said fourth generating means when saidspeed and direction sensing means senses the rotation of said motor tobe opposite the direction of rotation called for by said first controlmeans, second control means having an input connected to said fourthgenerating means and an output connected to said second generating meansfor controlling the period of conduction of said first controlledrectifying means, dynamic braking means responsive to said speed anddirection sensing means for applying an input to said second controlmeans when said speed and direction sensing means senses the directionof rotation of the motor to be opposite the direction of rotation calledfor by said first control means to enable said second control means toeffect conduction of said first controlled rectifying means at apredetermined minimum level to thereby dynamically brake the rotation ofthe motor, power supply means connected to the power source for applyingpredetermined potentials, and bypass means for rendering said firstcontrolled rectifying means nonconductive and connecting the powersource directly to the motor when said first control means is actuatedto a full speed condition.

2. A control system for controlling energy directed from a power sourceto a motor as defined in claim 1 wherein said commutating circuit meansincludes a second controlled rectifying means and energy storage meansconnected parallel to said second controlled rectifying means, saidenergy storage means being charged to a first polarity and charging to asecond polarity opposite said first polarity upon conduction of saidsecond controlled rectifying means, said energy storage means whenhaving said second polarity, reverse biasing said first and secondcontrolled rectifying means to render said controlled rectifying meansnonconductive.

3, A control system for controlling energy directed from a power sourceto a motor as defined in claim 2 wherein said energy storage meansincluding an inductor and a capacitor series connected to form a LC resonant circuit, said second controlled rectifying means being connectedparallel to said first controlled rectifying means, said LC resonantcircuit being connected parallel to said second controlled rectifyingmeans, said capacitor charging to a first polarity when said secondcontrolled rectifying means is nonconductive and discharging throughsaid inductor and said second controlled rectifying means uponconduction of said second controlled rectifying means, said capacitorcharging to a second polarity, opposite said first polarity, upondischarge thereof through said inductor and said second controlledrectifying means, said capacitor when charged to said second polarityreverse biasing said first and second controlled rectifying means torender said first and second controlled rectifying means nonconductive.

4. A control system for controlling energy directed from a power sourceto a motor as defined in claim 1 wherein said power supply meansincludes an astable multivibrator and a diode-capacitor matrix connectedto the output of said astable multivibrator for applying a regulatedvoltage to said second control means,

5. A control system for controlling energy directed from a power sourceto a motor as defined in claim 4 wherein said astable multivibratorincludes first and second NAND gates connectable to the power source,each of said NAND gates having first and second output conditions, saidfirst NAND gate having said first output condition when said second NANDgate has said second output condition and said first NAND gate havingsaid second output condition when said second NAND gate has said firstoutput condition, and said diode-capacitor matrix includes a firstcapacitor connected to the output of said first NAND gate, a secondcapacitor connected to the output of said second NAND gate, and a thirdcapacitor connected to said first and second capacitors for applying apredetermined voltage, said first capacitor charging when said firstgate is in said first condition and discharging when said first gate isin said second condition, said second capacitor charging when saidsecond gate is in said first condition and discharging when said secondgate is in said second condition, said third capacitor being charged bysaid first capacitor when said first NAND gate is in said secondcondition and being charged by said second capacitor when said secondNAND gate is in said second condition, said third capacitor beingcharged by said first and second capacitors to a predetermined negativepotential with respect to the power source.

6. A control system for controlling energy directed from a power sourceto a motor as defined in claim 5 wherein said power supply furtherincludes a Zener diode connected parallel to said third capacitor forregulating the negative output voltage applied by said third capacitor.

7. A control system for controlling energy directed from a power sourceto a motor as defined in claim 4 wherein said commutating circuit meansincludes a second controlled rectifying means and energy storage meansconnected parallel to said second controlled rectifying means, saidenergy storage means being charged to a first polarity and charging to asecond polarity opposite said first polarity upon conduction of saidsecond controlled rectifying means, said energy storage means whenhaving said second polarity reverse biasing said first and secondcontrolled rectifying means to render said controlled rectifying meansnonconductive.

8. A control system for controlling energy directed from a power sourceto a motor including a first controlled rectifying means connected tothe motor for controlling the energization thereof by pulse widthmodulation, a firing pulse generator connected to the gate of said firstcontrolled rectifying means for periodically rendering said firstcontrolled rectifying means conductive, a commutating circuit includinga second controlled rectifying means connected parallel to said firstcontrolled rectifying means, a resonant circuit connected parallel tosaid second controlled rectifyin g means, a commutating pulse generatorconnected to the gate of said second controlled rectifying means forperiodically rendering said second controlled rectifying meansconductive, said resonant circuit acting upon conduction of said secondcontrolled rectifying means to reverse bias said first controlledrectifying means thereby rendering said first controlled rectifyingmeans nonconductive, first control means for determining the directionof rotation of said motor, plug sensing means for sensing when the motoris rotating in a direction opposite to that called for by said firstcontrol means and dynamic braking circuitry for maintaining said firingpulse generator operating at a predetermined minimal value while themotor is traveling in a direction opposite that called for by the firstcontrol means to dynamically brake the motor.

9. A control system for controlling energy directed from a power sourceto a motor as defined in claim 8 further including a regulated negativepower supply including an astable multivibrator connected to the powersource and a diode-capacitor matrix connected to the output of saidastable multivibrator for directly inverting the power supplied to saidastable multivibrator by the power source to produce a negative outputvoltage.

10. A control system for controlling energy directed from a power sourceto a motor as defined in claim 8 further including an oscillator, asawtooth generator, and a reference operational amplifier, for producinga DC control signal at the output thereof, said output of said referenceoperational amplifier being summed with the output of said sawtoothgenerator and being applied to said firing pulse generator, said summedoutput of said sawtooth generator and said reference operationalamplifier actuating said firing pulse generator upon exceeding apredetermined threshold voltage to thereby effect conduction of saidfirst controlled rectifying means, said commutating pulse generatorhaving an input from said oscillator and actuating said commutatingcircuit at the end of each cycle of said oscillator.

1 1. A control system for controlling energy directed from a powersource to a motor as defined in claim 10 further including a referenceramp generator, for

producing an output applied to a positive input of said referenceoperational amplifier and a maximum current limit circuit for sensingthe current flow through the motor and applying a negative input signalto the positive input of said reference operational amplifier.

12. A control system for controlling energy directed from a power sourceto a motor as defined in claim 1 1 wherein said plug sensing means hasan output directed to said reference ramp generator when the motor isrotating in a direction opposite to that called for by said firstcontrol means to effect a substantially zero output from said referenceramp generator and said dynamic braking circuitry responsive to theoutput of said reference ramp generator, said dynamic braking circuitryhaving an output therefrom directed to the positive input of saidreference operational amplifier when the output of said reference rampenerator oes to substan rally zero, said output of san dynamic rakingcircuit effecting a minimal output from said reference operationalamplifier to enable the summed output, of said reference operationalamplifier and said sawtooth generator to exceed the threshold voltage ofsaid firing pulse generator to thereby effect firing of said firstcontrolled rectifying means to dynamically brake the motor when it istraveling in a direction opposite to that called for by said firstcontrol means 13. A control system for controlling energy directed froma power source to a motor as defined in claim 9 further including bypasscircuit means, said bypass circuit means including a pair of normallyopen contacts connected parallel to said first controlled rectifyingmeans, said contacts closing in response to an output from said bypasscircuit means to apply full potential from the power source to themotor, means responsive to the speed of the motor for closing saidcontacts when the motor is running at full speed and means for renderingsaid first controlled rectifying means nonconductive when the motor isrunning at the full speed.

14. A control system for controlling energy directed from a power sourceto a motor as defined in claim 9 further including first control meansincluding at least a pair of contacts connected to the motor foreffecting energization thereof and delay circuit means for delaying theoutput of said firing pulse generator after clos ing of said contacts toprevent bouncing of said contacts from interfering with the energizationof the motor.

2 222 UNETED STATES PATENT @ERTEFIfiATE G (IQRREQTIQN Patent No 3,710,216 Dated 1/9/73 Inventor(s) A. H. Smith It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

Col. 4, line 5: After "field" insert-22--.

Pg. 6, line 25:

C01. 4, line 19: I After "SCR" insert--24---.

Pg. 7, line 8:

Col. 4, line 36 After "sawtooth" eneratorshould Pg. 7, line 29: read---generator.

Col. 7, line 24: After "sensing" insert---circuit--.

Pg. 12, line 29:

C01. 7, lihe 33: "referee" should be--reference--.

Pg. 13, line 6: I

Col. 7, line 36: After "will" insert-be-.

Pg.l3, line 9:

Col. 12, lines 6-8: Delete ---This effectively reverse--- Pg. 21, line22: ---the anodes thereof.. This is a repeat. 7

Signed and sealed thi's 29th day of May 1975.

.LSEALl o Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK J Attesting Officer Commissionerof Patents 533 Wrat smrrs mm mm @ERTEIWQATE @E CQRREQTEQN Patent No;3,710,216 Dated 1/9/73 Inventor(s) A- H. Smith It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below: 7

Col. 4, line 5: After "field" insert--22--. Pg. 6, line 252' Col. 4,line 19: I After "SCR" insert---24-. Pg. 7, line8:

Col. 4, line 36 After "sawtooth" -eneratorshould Pg. 7, line 29: read---generator--.

Col. 7, line 24: After "sensing" insert--circuit-. Pg. 12, line 29:

Col. 7, lihe 33: "referee" should be---reference--.

Pg. 13, line 6:

Col, 7, line 36': After "will" insert---be-'. Pg.l3, line 9:

Col. 12, lines 6-8: Delete -This effectively reverse-- Pg. 21, line 22---the anodes thereof.'--. This is a repeato Signed and sealed this 29thday of May 1973.

Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTS CHALK J Att'esting OfficerCommissioner of Patents

1. A control system for controlling energy supplied from a power sourceto a motor comprising first controlled rectifying means having aconductive and nonconductive condition connected to the motor forcontrolling the energization thereof, first generating means forgenerating a plurality of repetitive pulses of a predetermined period,second generating means connected to said first generating means fordirecting firing pulses to said first controlled rectifying means torender said first controlled rectifying means conductive at apredetermined time during each of said predetermined periods, thirdgenerating means for generating commutating pulses, commutating circuitmeans responsive to said third generating means for rendering said firstcontrolled rectifying means nonconductive at the end of each of saidpredetermined periods, fourth generating means for generating a rampsignal upon acceleration of the motor from a zero speed condition, firstcontrol means for controlling the direction of rotation and the speed ofthe motor, speed and direction sensing means for affecting asubstantially zero output from said fourth generating means when saidspeed and direction sensing means senses the rotation of said motor tobe opposite the direction of rotation called for by said first controlmeans, second control means having an input connected to said fourthgenerating means and an output connected to said second generating meansfor controlling the period of conduction of said first controlledrectifying means, dynamic braking means responsive to said speed anddirection sensing means for applying an input to said second controlmeans when said speed and direction sensing means senses the directionof rotation of the motor to be opposite the direction of rotation calledfor by said first control means to enable said second control means toeffect conduction of said first controlled rectifying means at apredetermined minimum level to thereby dynamically brake the rotation ofthe motor, power supply means connected to the power source for applyingpredetermined potentials, and bypass means for rendering said firstcontrolled rectifying means nonconductive and connecting the powersource directly to the motor when said first control means is actuatedto a full speed condition.
 2. A control system for controlling energydirected from a power source to a motor as defined in claim 1 whereinsaid commutating circuit means includes a second controlled rectifyingmeans and energy storage means connected parallel to said secondcontrolled rectifying means, said energy storage means being charged toa first polarity and charging to a second polarity opposite said firstpolarity upon conduction of said second controlled rectifying means,said energy storage means when having said second polarity, reversebiasing said first and second controlled rectifying means to render saidcontrolled rectifying means nonconductive.
 3. A control system forcontrolling energy directed from a power source to a motor as defined inclaim 2 wherein said energy storage means including an inductor and acapacitor series connected to form a LC resonant circuit, said secondcontrolled rectifying means being connected parallel to said firstcontrolled rectifying means, said LC resonant circuit being connectedparallel to said second controlled rectifying means, said capacitorcharging to a first polarity when said second controlled rectifyingmeans is nonconductive and discharging through said inductor and saidsecond controlled rectifying means upon conduction of said secondcontrolled rectifying means, said capacitor charging to a secondpolarity, opposite said first polarity, upon discharge thereof throughsaid inductor and said second controlled rectifying means, saidcapacitor when charged to said second polarity reverse biasing saidfirst and second controlled rectifying means to render said first andsecond controlled rectifying means nonconductive.
 4. A control systemfor controlling energy directed from a power source to a motor asdefined in claim 1 wherein said power supply means includes an astablemultivibrator and a diode-capacitor matrix connected to the output ofsaid astable multivibrator for applying a regulated voltage to saidsecond control means.
 5. A control system for controlling energydirected from a power source to a motor as defined in claim 4 whereinsaid astable multivibrator includes first and second NAND gatesconnectable to the power source, each of said NAND gates having firstand second output conditions, said first NAND gate having said firstoutput condition when said second NAND gate has said second outputcondition and said first NAND gate having said second output conditionwhen said second NAND gate has said first output condition, and saiddiode-capacitor matrix includes a first capacitor connected to theoutput of said first NAND gate, a second capacitor connected to theoutput of said second NAND gate, and a third capacitor connected to saidfirst and second capacitors for applying a predetermined voltage, saidfirst capacitor charGing when said first gate is in said first conditionand discharging when said first gate is in said second condition, saidsecond capacitor charging when said second gate is in said firstcondition and discharging when said second gate is in said secondcondition, said third capacitor being charged by said first capacitorwhen said first NAND gate is in said second condition and being chargedby said second capacitor when said second NAND gate is in said secondcondition, said third capacitor being charged by said first and secondcapacitors to a predetermined negative potential with respect to thepower source.
 6. A control system for controlling energy directed from apower source to a motor as defined in claim 5 wherein said power supplyfurther includes a Zener diode connected parallel to said thirdcapacitor for regulating the negative output voltage applied by saidthird capacitor.
 7. A control system for controlling energy directedfrom a power source to a motor as defined in claim 4 wherein saidcommutating circuit means includes a second controlled rectifying meansand energy storage means connected parallel to said second controlledrectifying means, said energy storage means being charged to a firstpolarity and charging to a second polarity opposite said first polarityupon conduction of said second controlled rectifying means, said energystorage means when having said second polarity reverse biasing saidfirst and second controlled rectifying means to render said controlledrectifying means nonconductive.
 8. A control system for controllingenergy directed from a power source to a motor including a firstcontrolled rectifying means connected to the motor for controlling theenergization thereof by pulse width modulation, a firing pulse generatorconnected to the gate of said first controlled rectifying means forperiodically rendering said first controlled rectifying meansconductive, a commutating circuit including a second controlledrectifying means connected parallel to said first controlled rectifyingmeans, a resonant circuit connected parallel to said second controlledrectifying means, a commutating pulse generator connected to the gate ofsaid second controlled rectifying means for periodically rendering saidsecond controlled rectifying means conductive, said resonant circuitacting upon conduction of said second controlled rectifying means toreverse bias said first controlled rectifying means thereby renderingsaid first controlled rectifying means nonconductive, first controlmeans for determining the direction of rotation of said motor, plugsensing means for sensing when the motor is rotating in a directionopposite to that called for by said first control means and dynamicbraking circuitry for maintaining said firing pulse generator operatingat a predetermined minimal value while the motor is traveling in adirection opposite that called for by the first control means todynamically brake the motor.
 9. A control system for controlling energydirected from a power source to a motor as defined in claim 8 furtherincluding a regulated negative power supply including an astablemultivibrator connected to the power source and a diode-capacitor matrixconnected to the output of said astable multivibrator for directlyinverting the power supplied to said astable multivibrator by the powersource to produce a negative output voltage.
 10. A control system forcontrolling energy directed from a power source to a motor as defined inclaim 8 further including an oscillator, a sawtooth generator, and areference operational amplifier, for producing a DC control signal atthe output thereof, said output of said reference operational amplifierbeing summed with the output of said sawtooth generator and beingapplied to said firing pulse generator, said summed output of saidsawtooth generator and said reference operational amplifier actuatingsaid firing pulse generator upon exceeding a predetermined thresholdvoltage to thereby effecT conduction of said first controlled rectifyingmeans, said commutating pulse generator having an input from saidoscillator and actuating said commutating circuit at the end of eachcycle of said oscillator.
 11. A control system for controlling energydirected from a power source to a motor as defined in claim 10 furtherincluding a reference ramp generator, for producing an output applied toa positive input of said reference operational amplifier and a maximumcurrent limit circuit for sensing the current flow through the motor andapplying a negative input signal to the positive input of said referenceoperational amplifier.
 12. A control system for controlling energydirected from a power source to a motor as defined in claim 11 whereinsaid plug sensing means has an output directed to said reference rampgenerator when the motor is rotating in a direction opposite to thatcalled for by said first control means to effect a substantially zerooutput from said reference ramp generator and said dynamic brakingcircuitry responsive to the output of said reference ramp generator,said dynamic braking circuitry having an output therefrom directed tothe positive input of said reference operational amplifier when theoutput of said reference ramp generator goes to substantially zero, saidoutput of said dynamic braking circuit effecting a minimal output fromsaid reference operational amplifier to enable the summed output of saidreference operational amplifier and said sawtooth generator to exceedthe threshold voltage of said firing pulse generator to thereby effectfiring of said first controlled rectifying means to dynamically brakethe motor when it is traveling in a direction opposite to that calledfor by said first control means.
 13. A control system for controllingenergy directed from a power source to a motor as defined in claim 9further including bypass circuit means, said bypass circuit meansincluding a pair of normally open contacts connected parallel to saidfirst controlled rectifying means, said contacts closing in response toan output from said bypass circuit means to apply full potential fromthe power source to the motor, means responsive to the speed of themotor for closing said contacts when the motor is running at full speedand means for rendering said first controlled rectifying meansnonconductive when the motor is running at the full speed.
 14. A controlsystem for controlling energy directed from a power source to a motor asdefined in claim 9 further including first control means including atleast a pair of contacts connected to the motor for effectingenergization thereof and delay circuit means for delaying the output ofsaid firing pulse generator after closing of said contacts to preventbouncing of said contacts from interfering with the energization of themotor.